On average it costs more than $2 Billion to take a single drug from discovery to regulatory approval. Animal testing is a mandatory, time-consuming and costly step that needs to be passed in this journey. Other than ethical issues normally exists with animal studies, its results cannot precisely predict what happens in human. By Human organ-on-chips researchers are hoping to replace animal testing and not just mimic cell functions, but mimic a human organ-level or ideally human body-level functions. With such platform, disease and organ functions and physiology can be modeled on a small chip and discovered drugs can be screened, leading to significant decrease in drug development time and cost. So, unsafe and inefficient drugs fail cheaply and early before entering the clinical trial phase as the most expensive and time-consuming phase of a drug development. Organ-on-chips are usually microfluidics devices that embedded with extra parts and equipment to provide physiological movements, blood flow and so on. Using patients' own cells, organ-on-a-chip system is hopped to pave the way to personalized medicine.